The present invention relates to the field of casters for providing rolling support of objects, and more particularly concerns casters that may support swinging doors.
Casters are often used to provide rolling support for loads in a variety of applications. In general, casters include a kingpin mounted to an object, a bracket mounted to the kingpin, an axle mounted to the bracket, and a wheel or roller mounted to the axle. The bracket, axle, and wheel may swivel around the kingpin.
Casters are often used with doors, gates, or other similar hinged, swinging objects. Doors may sag at their free vertical edge, as hinges do not always maintain the door in the originally installed alignment. Sagging becomes an increasingly significant issue for heavy and wide doors, resulting in a larger moment about the hinges. Casters are mounted to the door such that the roller is positioned between the bottom edge of the door and the floor, typically adjacent the free vertical edge of the door. The caster allows swinging movement of the door between closed and open positions while providing uplifting force to place and maintain the door in position.
Some casters used for doors, gates, or the like, may also include a coil or leaf spring to allow vertical displacement of the roller relative to the door to maintain contact with the floor, in case of variation in elevation of the floor relative to the door, as the door swings. The coil-type spring may be disposed around a telescoping kingpin or other similar arrangement. Alternatively, the spring may be leaf-type, being wrapped around an axle on each side of a roller. With such arrangements the orientation of the axle is perpendicular to the longer dimension of the leaf spring, and the direction of the movement of the roller is aligned with the longer dimension of the leaf spring.
In some cases, for aesthetic reasons, it may be desirable to conceal casters within the doors. Concealed casters may be desirable in, for example, heavy, wide, commercial doors in high-end offices, but may also be desirable elsewhere. Concealment requires that the caster fit within the thickness of a door. Most often the caster arrangement on doors is disposed in plain view.
Accordingly, there exists a need for a new caster for a door. Ideally, the new caster may be substantially concealed in the door, and may maintain contact with the floor over the extent of the door's movement.